The general surface may be characterized as of comparatively low-relief, the hills not often rising over 200 feet, but here and there over the country are conspicuous elevations, visible at long distances, which form useful landmarks and from whose summits comprehensive birds-eye impressions of the surrounding country are possible. Structurally they appear to be, in a few cases, resistant knobs of Keewatin, which project well above the general peneplain level, but more commonly they are tilted ridges of Huronian. A characteristic representative of the latter type forms a long ridge beginning a mile and a quarter north-east of Duncan lake and extending thence for several miles in a north-easterly direction. The south-east side of this ridge slopes gently at an angle corresponding with the dip of the beds, but the north-west face is an abrupt cliff dropping almost perpendicularly for about 400 feet to a flat sandy plain which extends westward and northward for several miles, beyond which are other monadnock-like knobs. The accompanying diagram is intended to represent the structure in vertical cross-section.
[Illustration: Fig. 2.—Vertical section across Huron Ridge, North of Duncan Lake.]
Another ridge of similar character, standing 550 feet above the level of Duncan lake, is visible from the ridge just described and from points on Duncan and Otto lakes, and adjoining country. Its position as indicated on the map is about four miles north of the large island in the middle of Duncan lake, a view of it from this point being shown in fig. 4. In this case the east face is perpendicular. A prominent hill of the same kind is visible from Obushkong lake, lying a short distance to the north-west of that body. Just west of Mosher lake as represented in fig. 5, two round hills of about equal size rise 300 feet above the water level. The more southerly of the two is of Keewatin, while that to the north is composed wholly of diabase, Huronian lying around the base of each. Bold, but less individualized elevations are common in the neighbourhood of Kenisheong lake, and other localities. All these hills are markedly rocky and free from soil.
Less conspicuous than these great masses are certain minor, but persistent features which are directly referable to geological conditions. Within Huronian areas there is a distinct tendency toward the development of a system of parallel ridges similar in structure and mode of origin to the hill at the north-east of Duncan lake. This feature is developed with special regularity in the southern part of the wedge between Duncan lake and the West branch, where a succession of north and south ridges alternate with strips of swampy ground. The western faces of the ridge are bare and cliff-like, while the eastern slopes are gentle, well soil-covered and forested.